1. Field Of The Invention
This invention relates, in general, to water sprinkling systems and, more specifically, to electrical control apparatus for automatically controlling the release of water in a water sprinkling system.
2. Description Of The Prior Art:
It is well known to water lawns, plants, crops, etc., by use of an irrigation or sprinkling system in which water is admitted through a control valve to a plurality of pipes, hoses or conduits extending over the lawn or field and subsequently through a sprinkler device attached to the end of the conduits for dispersing water over the area to be watered.
In those sprinkling systems utilizing a manually operated control valve, the control valve is left open until the soil is assumed to be sufficiently moist. This depends on guesswork and, even if efficiently handled, commonly results in over-watering thereby damaging the plants and wasting water or under-watering, again possibly damaging the plants, grass or crops.
Automatically operated valves have also been deviced for sprinkler systems in which the valve is opened to permit water to flow through the sprinklers at preset times during the day or night for a predetermined amount of time. However, such automatic control valves still suffer from indiscriminate operation without regard to the actual moisture content of the soil.
It is also known to utilize sensing devices with such automatic sprinkling systems to selectively control the energization of such sprinkling systems with respect to the actual moisture content of the soil. Such sensing devices utilize a pair of spaced probes which are placed vertically into the ground within the area to be watered. The probes measure the conductivity or resistance of the soil which is proportional to the moisture content of the soil. When the sprinkler control system is energized manually or by a master timer at a preset time during the day, the soil conductivity is measured and, if below a preset minimum value, the sprnklers are turned on until the probes detect a preset conductivity. The sprinklers are then turned off. If the soil conductivity, when measured, is above a preset minimum, indicating sufficient moisture content, the sprinkler system is not energized.
Although the latter types of sprinkler control systems provide more efficient utilization of water and a more thorough watering of the soil, they are not without drawbacks. In such sprinkler systems, the reference levels are set to ensure a saturated moisture condition in order to maximize the moisture content in the soil. This wastes water since a saturated amount of water in the soil is not necessary for efficient plant growth. Furthermore, such control systems are dependent upon the soil conditions, whether the soil is acidic or basic, and the type of water available in the area which determines the amount of water that is dissolvable in the soil. Due to the presence of various types of soil conditions within a small portion of a given area, over or under-watering can still result. Furthermore, since previously deviced sensors comprise a pair of rods placed vertically in the ground, misplacement commonly occurs. For these reasons, such automatic control systems have not found widespread use.
Thus, it would be desirable to provide a control apparatus for an automatic water sprinkler system which overcomes the problems of similar prior art sprinkler control devices. It would be desirable to provide a control apparatus for sprinkler systems which provides a precise amount of water for various types of soil conditions. It would also be desirable to provide a control apparatus for sprinkler systems which provides only the amount of water required for maximum plant growth. It would also be desirable to provide a control apparatus for sprinkler systems which can be easily added onto an existing sprinkler control system. It would also be desirable to provide a control apparatus for sprinkler systems which is usable with multi-zone, indexing-type sprinkler systems. Finally, it would be desirable to provide a control apparatus for sprinkler systems which provides proper sensor placement in the soil.